In general, a long trim is attached along a flange at an opening edge of a door or a window of a vehicle such as an automobile. The trim is made by extruding polymer material such as rubber or thermoplastic synthetic resin (including thermoplastic elastomer) into a shape having a mounting portion with a substantially U-shaped cross section. The trim is fixed to the flange as the substantially U-shaped mounting portion nips the flange. The mounting portion of the trim can be reinforced with a core and stably fixed to the flange at the opening edge by embedding a long reinforcing core (for example, a metal plate such as a cold rolled steel plate) having a substantially U-shaped cross section in the mounting portion and integrating the core with the mounting portion.
A flange at an opening edge of a door or a window of a vehicle is two-dimensionally or three-dimensionally curved in a longitudinal direction. Thus, a trim, which has been formed by extrusion so as to be substantially linear, is bent so that the trim fits the curve of the flange at the opening edge and attached to the flange. Therefore, as a core to be embedded in a trim, a partially punched core (also referred to as a fish-bone core or a keel core), which has spaces at a predetermined interval in a longitudinal direction, is used so that the core can be flexibly bent to follow the bend of the trim.
However, when a trim with an embedded core is made by covering the partially punched core with a trim polymer material, recessed marks (also referred to as keel marks) may occur on a surface of the trim at a predetermined interval in the longitudinal direction, which may deteriorate the appearance of the trim. The recessed marks occur more conspicuously when the thickness of the core is increased and the ratio of the thickness of the core to the thickness of a trim polymer material covering the core is increased so as to increase the retention strength of the trim.
Presumably, the recessed marks occur for the following reason. The spaces, which are formed in the partially punched core at a predetermined interval, usually have a width in the longitudinal direction as narrow as about 1 mm. Thus, when flowing the trim polymer material into the spaces, the flow resistance is large, which makes it difficult to flow a sufficient amount of polymer material into the spaces. Moreover, regarding the trim polymer material covering the core, the thickness of the polymer material at portions corresponding to the spaces (portions where the core is absent) is larger than the thickness at portions where the core is present, which leads to larger mold shrinkage of the polymer material. Therefore, the recessed marks presumably occur on the surface of the trim in the portions corresponding to the spaces of the core (portions where the core is absent).
In order to address the problem that the appearance deteriorates due to occurrence of the recessed marks, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 9-76835) describes a trim in which a plurality of ribs extending in a longitudinal direction are formed in portions of the trim, the portions covering slits (spaces) of a core, and the ribs are covered with sponge rubber, so that recessed marks occurring on the trim with an embedded core are made inconspicuous.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-76835 (p. 2, etc.)